#include<iostream>
using namespace std;
int main(){
  double n;
  cin>>n;
  double l=-10000,r=10000;
  while(r-l>1e-8){
    double mid=(l+r)/2;
    if(mid*mid*mid<n)l=mid;
    else r=mid;
  }
  cout<<fixed;
  cout.precision(6);
  cout<<l;
}